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la  dernldre  page  qui  comporte  une  telle 
empreinte. 

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et  de  haut  en  bas,  en  prenant  le  nombre 
d'Images  ndcessaire.  Les  diagrammes  suivants 
illustrent  la  m^thode. 


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4  5  6 


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Reprinted  from  The  Journal  of  Geology,  Vol.  II.,  No.   i 
January-February,  1894 


THE  DISTRIBUTION  OF 

Ancient  Volcanic  Rocks 

ALONG  THE  EASTERN 
BORDER  OF 

A^ORTH  America 


1 


i^l 


_4^^' 


w 


\ 


GEORGE  HF  WILLIAMS 


I'l 


i 


CHICAGO 
D.  C.  HEATH  &  CO.,  Directors 


01 


'l.ATli    I. 


I'l.ATK    I. 


[ 


!.»»* 


THE 
ROBABLB 

ES    OF 

NIC  ROCKS 
rH  AMEBICA 

ON  WILLIAMS 


I  PROBABLE 

Bntdirl  i  Co..  Engr>;  Chi, 


With  the  campltments  at 

George  Huntindtdn  Williams, 

Johns  Hopkins  University, 

UALTIMHRE,  MIJ. 


JOURNAL  OF  GEOLOGY 

JANUARY-FEBRUARY,  1894. 


THE  DISTRIBUTION  OF  ANCIENT  VOLCANIC  ROCKS 

ALONG  THE  EASTERN  BORDER  OF 

NORTH  AMERICA.' 


CONTENTS. 

Introduction. 

Diversity  of  Opinion  regarding  Ancient  Volcanic  Rocks, 

Great  Britain. 

Germany. 

Belgium  and  France. 

Scandinavia. 

Russia. 

America. 
Criteria  for  the  recognition  of  Ancient  Volcanic  Rocks. 
Distribution  of  Volcanic  Areas  in  Eastern  North  America. 

Eastern  Canada  (Newfoundland,  Cape  Breton,  Nova  Scotia,  Gasp^,  New 
Brunswick,  Eastern  Townships). 

New  England  States  (Maine,  New  Hampshire,  Massachusetts). 

Middle  Atlantic  States  (New  York,  Pennsylvania,  Maryland,  Virginia). 

Southern  States  (North  Carolina,  South  Carolina,  Georgia,  Alabama). 
General  Conclusions. 


The  great  crystalline  belt  of  the  Eastern  United  States  and 
Canada,  in  spite  of  all  the  attention  it  has  received,  is  probably 
still  the  least  understood  geological  province  of  our  continent. 
Here,  alniost  more  than  anywhere  else,  personal  adherence  to 
some  preconceived  theory  of  the  origin  and  relationships  of  rocks 
has  biased  observation  and  led  to  contradictory  or  unsatisfactory 

•  This  paper  was  outlined  at  the  International  Geological  Congress  in  Chicago, 
August,  1893,  »nd  read  in  full  before  the  Geological  Society  of  America  at  its  Boston 
Meeting,  December  28,  1893. 
Vol.  II.,  No.  I.  i 


THE  JOURNAL  OF  GEOLOGY. 


interpretations  of  the  facts.  Only  within  recent  years  has 
detailed  and  independent  work  been  undertaken  in,  widely  sepa- 
rated parts  of  this  vast  area,  and  as  yet  no  sufficient  data  is  at 
hand  for  stru  tural,  or  even  for  petrographical  correlation 
throughout  the  whole. 

Complete  geological  maps,  showing  the  structural  relations 
and  chronological  sequence  of  all  the  crystalline  formations,  are 
undoubtedly  what  must  be  looked  forward  to  as  the  ultimate  aim 
of  work  within  this  region,  but  the  most  sanguine  will  surely 
admit  that  we  are  at  present  a  long  way  from  any  such  reality. 
Meanwhile,  in  the  absence  of  paleontological  evidence,  the  study 
of  the  rocks  from  the  point  of  view  of  genesis  and  the  establish- 
ment of  petrographic  correlations  will  do  much  toward  furnish- 
ing the  positive  basis  of  knowledge  upon  which  final  solution  of 
complex  structure  must  rest. 

Some  of  the  notions  regarding  petrographic  sequence  and 
the  origin  of  foliation,  enforced  by  masters  of  geology  high  in 
authority,  have  obscured  rather  than  advanced  the  problems  pre- 
sented by  the  crystalline  rocks  in  eastern  North  America.  Not 
only  have  we  been  taught  that  the  mineralogical  and  structural 
characters  of  these  rocks  are  safe  indices  of  their  superposition 
and  relative  age,  but  the  interpretation  of  all  parallel  structures 
as  proofs  of  sedimentation  has  led  to  the  conclusion  that  igneous 
rocks  are  rare,  if  not  altogether  absent,  in  these  oldest  and  gen- 
erally foliated  formations  of  the  earth's  crust.  Now,  however, 
better  conceptions  are  beginning  to  prevail.  No  longer  do  we 
regard  the  petrographic  character  of  a  crystalline  rock  as  any 
criterion  of  its  age,  while  modern  methods  have  enabled  us  to 
identify  the  abundant  igneous  rocks  of  ancient  times  in  spite 
of  the  misleading  structures  imparted  to  them  by  secondary 
causes. 

Object  of  this  paper. — The  present  writer  has  had  frequent 
occasion  to  insist  on  the  presence  of  such  disguised  igneous 
masses  in  the  oldest  geological  formations,  and  to  dwell  upon 
the  methods  by  which  their  origin  may  be  established.  In  the 
present  paper  it  is  his  object  to  show  that  not  only  igneous,  but 


11 


THE  D/STRinUT/OX  OF  ANCIENT  VOLCANIC  ROCK'S.       3 

also  volcanic'  rocks  arc  widely  distributed  tiirough  the  crystalline 
belt  of  eastern  North  America,  and  to  direct  attention  to  them  as 
offering  a  new  and  promising  field  for  work  in  crystalline  geol- 
ogy. For  tho  accomplishment  of  this  purpose  it  will  be  neces- 
sary ''i)  to  consider  the  general  attitude  of  geologists  in  differ- 
ent countries  toward  ancient  volcanic  rocks;  (2)  to  specify  the 
criteria  c-vailable  fpr  their  identification ;  and  (3)  to  summarize 
our  present  knowledge  of  where  such  rocks  certainly  or  probably 
exist  in  the  eastern  crystalline  belt.  The  material  embraced 
under  the  third  of  these  heads  has  been  obtained  from  personal 
work  in  th'-'  field,  from  a  careful  study  of  existing  literature,  and 
from  unpublished  observations  and  hints  furnished  by  friends.* 

It  is  hoped  that  the  bringing  together  of  what  is  now  known 
of  the  distribution  of  ancient  volcanic  rocks  in  eastern  North 
America,  with  the  addition  of  new  areas  and  indication  of  locali- 
ties where  they  may  be  looked  for,  will  stimulate  further  work 
in  widely  separated  portions  of  this  interesting  field.  These 
rocks  have,  it  is  true,  already  been  correctly  described  at  a  few 
isolated  points,  but  no  attempt  has  before  been  made  to  connect 
such  areas  or  to  show  their  probably  widespread  distribution. 
The  recent  identification  by  the  writer  of  a  very  extensive  devel- 
opment of  pre-Cambrian  lavas  and  volcanic  tuffs  and  breccias  in 
the  South  Mountain  of  southern   Pennsylvania  and  MarylandJ 

» The  term  volcanic  might,  perhaps  be  applied  with  propriety  to  all  rocks  pro- 
duced  in  or  on  a  volcano,  without  regard  to  their  structure  or  coarseness  of  grain.  It 
is,  however,  here  employed  only  for  effusive  or  surface  igneous  rocks,  in  contrast  to 
such  as  have  so'!.;ified  beneath  the  surface,  either  as  the  basal  portions  of  volcanoes, 
or  as  dykes,  -,!     -     laccolites,  or  stocks  (bathylites). 

»  The  writer  especially  indebted  for  help  to  Professor  Eugene  Smith  of  Ala- 
bama  ;  Professor  W.  S.  Bayley,  of  Waterville,  Me.;  Professor  J.  A.  Holmes,  of  North 
Carolina ;  Professor  H.  D.  Campbell,  of  Lexington,  Va.;  Dr.  A.  C.  R.  Selwyn  of 
Ottawa ;  Mr.  L.  V.  Pirsson,  of  New  Haven ;  Professor  S.  L.  Powell,  of  Newberry 
South  Carolina,  and  Mr.  Arthur  Keith,  of  Washington.  The  "  Azoic  System"  of 
Whitney  and  Wadsworth.  and  Professor  Van  Hise's  Correlation  Essay  on  the  Algon- 
kian  have  also  proved  of  much  service. 

3  Am.  Jour,  of  Science  (3d  sen).  Vol.  44,  p.  495,  Dec.  1892.  These  rocks  have 
been  thoroughly  studied  by  Miss  Florence  Bascom,  whose  results  may  be  expected  soon 
to  appear  in  full  and  adequately  illustrated  form.  See  also  this  Journal,  Vol.  I  No  8 
Dec,  1893.  ■    ' 


\ 


,      I 


w^??s^»^-f«-iwsf?<!»ir^/!gj*?*:wrl;  -jraMt0^' 


4  THE  JOURNAL  OF  GEOLOGY. 

naturally  suggested  a  comparison  of  these  rocks  with  those  of 
similar  character  in  the  Boston  basin  and  eastern  Canada,  as  well 
as  a  further  search  for  other  regions  of  the  same  kind.  This 
search  has  already  proved  successful  in  North  Carolina  and 
Maine,  while  an  examination  of  the  older  literature  indicates 
many  other  places  where  a  recurrence  of  like  conditions  may  be 
confidently  expected. 

The  proper  interpretation  and  areal  mapping  of  all  the 
demonstrably  volcanic  regions  in  the  Appalachian  crystallines 
will  not  only  afford  much  material  of  interest  in  the  study  of 
petrography  and  dynamometamorphism,  but  will  also  contribute 
to  the  differentiation  and  final  understanding  of  the  vast  belt  of 
diverse  crystalline  rocks  to  which  they  belong. 

DIVERSITY    OF   OPINION    REGARDING    ANCIENT    VOLCANIC    ROCKS. 

There  is  notable  in  the  different  countries  where  geology 
is  cultivated  a  wide  diversity  of  opinion  regarding  ancient  vol- 
canic rocks.  In  some  regions  such  rocks  have  been  entirely 
overlooked  or  else  misinterpreted ;  in  others  they  are  recognized, 
but  are  conceived  as  having  been  formed  under  circumstances  so 
different  from  those  which  now  obtain  that  they  are  genetically 
and  inherently  distinct  from  the  products  of  modern  volcanoes ; 
in  a  few  only  are  they  considered  as  having  been  origin- 
ally identical  with  recent  effusive  rocks,  and  as  differing  from 
them  only  in  alterations  due  to  subsequent  causes.  This  diver- 
sity of  opinion  may  be  accounted  for  in  part  by  the  varying  state 
of  preservation  of  ancient  volcanic  material  in  different  parts  of 
the  earth's  surface  or  by  the  lack  of  experience  of  field  geolo- 
gists with  the  characteristic  features  of  modern  lavas.  It  is, 
however,  also  due  in  a  measure  to  the  persistence  of  certain 
ideas  promulgated  by  early  masters  of  the  science  in  their 
respective  lands. 

It  was  in  Great  Britain  that  the  real  nature  of  ancient  volcanic 
products  received  its  earliest  and  fullest  recognition.  In  spite 
of  the  absence  of  active  volcanoes  from  the  islands,  these  rocks 
have  from  the  earliest  days  of  geological  inquiry  been  favorite 


THE  DISTRIBUTION  OF  ANCIENT  VOLCANIC  ROCKS.      5 

subjects  of  investigation.  From  the  first,  their  essential  identity 
with  modern  volcanic  products  has  been  clearly  recognized  and 
repeatedly  insisted  upon — something  which  wc  may  attribute  to 
the  doctrines  of  Mutton  and  to  the  uniformitarian  principles  of 
Lyell.  Such  geologists  as  Scrope,  de  la  Beche,  Sedgv/ick, 
Murchison,  Jukes,  Lyell  and  Ramsay,  speak  continually  of  lava- 
flows,  tuffs,  breccias  and  ash-beds  in  a  way  that  implies  no  doubt 
in  their  minds  as  to  the  existence  of  volcanoes  like  those  now 
active,  in  Paleozoic  and  pre-Paleozoic  times.  And  more 
recently  the  delicate  methods  of  modern  petrography  have  in  the 
same  country  been  first  made  to  establish  the  identity  between 
ancient  volcanic  rocks  and  those  of  the  present.  The  world  is 
now  but  beginning  to  follow  in  this  respect  the  lead  set  by 
Allport,  J,  A.  Phillips,  Judd,  Bonney,  Rutley,  Marker,  Cole  and 
others  in  Great  Britain.  A  few  Englishmen,  like  Mallet  or 
Hicks,  have  considered  the  oldest  volcanic  rocks  either  as  orig- 
inally different  from  those  now  produced,  or  as  characteristic  of 
some  definite  geological  horizon,  but,  on  the  whole,  the  British 
school  of  geology,  more  than  any  other,  recognizes  a  practical 
uniformity  in  the  nature  of  volcanic  action  and  products  fi  i  n  the 
Archean  to  the  present.' 

In  Germany  and  France  volcanic  rocks  {Ergussgesteine)  are 
recognized  as  abundant  in  certain  of  the  earlier  geological  form- 
ations. Nevertheless  there  is  in  these  countries  a  prevailing  ten- 
dency to  separate  Tertiary  from  pre-Tertiary  rocks  of  this  class 
as  things  originally  and  genetically  distinct."  It  is  noticeable 
that  the  earlier  schemes  of  rock-classifici»lion,  like  those  of 
Brongniart,  Haiiy,  Cordier  and  K.  C.  von  Leonhard,  are  quite 
purely  mineralogical.  The  division  of  older  and  younger,  or 
paleo-  and  neo-volcanic  rocks  is  to  be  in  part  accounted  for  by 
the  concentration  of  these  masses  in  central  Europe  within  the 
Permo-Carboniferous  and  Tertiary  periods  and  their  comparative 

'  See  "The  History  of  Volcanic  Action  in  the  Area  of  the  British  Isles,"  Presiden- 
tial Address  by  Sir  Archibali  Geikie,  F.R.S.,  etc.  Quart.  Jour.  Geol.  Soc,  Vols.  47 
and  48,  1891-2. 

'Roth:  Sitzber.  Berl.  Ak.  1869,  p.  72,  et  stq.  Zirkel:  Lehrbuch  der  Petro- 
graphie,  2d.  ed.,  Vol.  I.,  p.  838,  1893. 


1 


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6  THE  JOURNAL  OF  GEOLOGY. 

rarity  in  Mcsozoic  times.  It  is,  however,  also  connected  with 
thcWcrncrian  tloctrine  of  the  non-recurrence  of  certain  physical 
conditions  in  the  earth's  tlcvelopnient,  as  contrasted  with  the 
uniformitarianism  of  Hutton  and  Lyell.  The  absence  of  vol- 
canic types  in  Europe  which  serve  to  bridge  over  the  sharp 
contrast  between  those  of  the  Carboniferous  and  Tertiary, 
is  being  rapidly  compensated  Iv  the  discovery  of  such  rocks  in 
other  regions.  Fortunate  finds  .f  even  pre-Cambrian  lavas  so 
perfectly  preserved  as  to  demonstrate  their  practical  identity, 
both  chemically  and  structurally,  with  recent  products  is  tending 
to  weaken  the  old  distinction  on  the  continent.  There  are  now 
many  signs  of  j)rogress  toward  the  idea  that  the  characters 
regarded  as  belonging  peculiarly  to  the  older  effusive  rocks  arc 
better  explained  through  changes  subsequent  to  their  solidifica- 
tion. 

Thus  Ludwig  in  1861,'  Vogelsang  in  1867,'  »"'^  Lossen  in 
1869,3  regard  some  quartz-porphyries  as  only  devitrified  glasses, 
identical  with  those  of  modern  volcanic  regions;  Kalkowsky,* 
and  recently  Sauer'  and  Vogel,*  have  also  brought  convincing 
proof  that  such  is  often  the  case. 

Gllmbel  says :  "  Es  scheint  in  dieser  Bezichung  denn  doch  eher  gerecht- 
fertigt,  zunachst  das  petrographisch  Gleiche  auch  gleich  zu  bezeichnen,  als  in 
einzelnen  FSllen  ein  neues  Princip,  das  des  Alters,  in  die  Petrographie  einzu- 
ftlhren,  welches  bei  den  meisten  Ubrigen  Fallen  nicht  verglichen  und  berlick- 
sicht  werden  kann  ; " ' 

And  Rosenbusch  also  remarks  : 

"  Man  hat  den  geologischen  Alter  der  Eruptivgesteine  bisher  ein  hSheres 
bestimmendes  Moment  fUr  die  structurelle  und  mineralogische  Ausbildung 
dieser  zugeschrieben  als  demselben  in  Wirklichkeit  zukommt."' 

■  Erl.  z.  geol.  Karte  Hessens,  Bl.  Dieburg,  p.  56,  1861. 

'Philosophie  der  Geologie,  pp.  144-146,  1867. 

3Abh.  Berl.  Ak.,  1869,  p.  85. 

^  TscHERMAK's  Min.  Mitth,  pp.  31  and  58,  1874. 

^Erl.  zur  geol.  Specialkarte  Sachsens,  Bl.  Meissen,  pp.  81-91,  1889 

'  Abh.  geol.  Landesanstalt  von  Hessen,  vol.  ii.,  p.  38,  1892. 

'  GrundzUge  der  Geologie,  1888,  p.  85. 

'Die  massigen  Gesteine,  2d.  ed.,  1887,  p.  4. 


■^ 


THE  DISTRllWriON  OF  ANCIENT  VOLCANIC  ROCKS,      7 

lie  nevertheless  adheres  to  the  division  between  paleo-  and 
nco-volcanic  rocks,  although  he  says  that  about  llieir  only  differ- 
ence iu  that  the  latter  can  often  be  found  to  belong  to  volcanoes 
(i.  e.,  volcanic  mountains)  which  are  themselves  so  extremely 
subject  to  removal  by  erosion.' 

Admirable  observations  on  the  use  of  age  in  rock-classifica- 
tion are  made  by  M.  Neumayr.     He  says: 

"  Wohl  IUUS8  dcr  Geolog  dem  Alter  der  Gesteine  Rechnunx  traKeii,  aber 
diese  HerlU  ksichtigung  ist  eine  von  der  Heschreibung  uiid  Eintheilung  der 
Gesteine  durchaus  unabhilngige  Sache.  Wie  schon  oft  betont  worden  ist,  ist 
uriter  den  Sedimentargesteinen  das  richtige  Prinzip  schon  durchgeflihrt, 
dass  man  von  Kalken,  von  Dolomiten,  Sandsteinen,  etc.,  des  Silur,  des  Jura, 
des  TertiSr  spricht,  ohne  die  verschiedenalterigen  Gesteine  von  gleicher 
lieschafifenheit  init  eigneii  Namen  zu  belegen  ;  genau  in  derselben  Wcise 
wird  man  auch  mit  den  Miissengesteinen  verfahren  mlissen.  Auf  einen 
solchen  Standpunkt  wird  und  muss  die  Gesteinslehre  ebenfalls  gelangen  ;  sie 
wird  ihre  Unterscheiduri'-  ler  Felsarten  nur  nach  petrographischen  Merk- 
malen  und  petrographischcr  Methodc  vornehmen,  und  die  Altersbestimmung 
derGeologieliberlassen,  was  natUrlichnicht  ausschliesst.dassbeide  Forschungs- 
gebiete  von  einer  und  derselben  Person  beherrscht  werden."' 

In  Belgium  we  see  de  la  ValleSe  Poussin  in  1885  writing  of 
"  Les  anciennes  Rhyolites  dites  Eurites,"  ^  just  as  they  would  in 
England  ;  while  in  France  the  recognized  leader  in  petrograph- 
ical  usage,  Michel-L6vy,  although  he  still  distinguishes  "  roches 
porphyriques  ante-tcrtiaires,"  from  "roches  trachytoides  tertiaires  et 
post-tertiaires,"  expresses  himself  in  regard  to  the  futility  of  the 
age  distinction  in  rock  nomenclature  as  follows  : 

"On  voit, par  tout  ce  qui  pr^c^de,  qu'il  est  n^cessaire  d'asseoir  une  classi- 
fication p^trograjihique  rationnelle  sur  des  faits  contingents,  independents 
d 'hypotheses  g^ogdn^tiques,  et  que  la  consideration  de  I'ftge  des  roches,  k  ce 
point  de  vue,  est  aussi  hypoth^tique  que  celle  de  leurs  conditions  degisement 
dans  les  profondeurs  ou  k  la  surface.  Etant  donn6  un  ^chantillon  de  pro- 
venance inconnue,  il  est  indispensible  et  il  est  possible  de  le  nommer  et  de  le 
d^crire  sans  amphibologie.  II  n'est  possible  d'en  determiner,  avec  certitude 
et  precision  ni  le  gisement  ni  I'ftge  geologique."* 

•lb.,  p.  6. 

'Erdgeschichte,  Vol.  I,  p.  599. 

sBull.  de  I'Acad.  roy.  de  Belgique  (3)  Vol.  10,  No.  8,  1885. 

<  Structures  et  Classification  des  Roches  Erupt! ves,  p.  34,  1889. 


.'.a^^^^aygi^'^M^Ljj^^w^^M^^^^u^^iggrg 


8  THE  JOURNAL  OF  GEOLOGY. 

In  Scandinavia,  if  we  judge  from  the  most  recent  publica- 
tions, there  is,  in  spite  of  the  general  adherence  to  German 
nomenclature,  a  fuller  recognition  of  the  similarity  between 
ancient  and  modern  volcanic  rocks  than  is  to  be  found  in  any 
other  part  of  Europe  except  England. 

On  the  western  coast  of  Norway,  Reusch  describes  old  lava 
flows  of  quartz-porphyry  and  more  basic  diabase  amygdaloids 
which  show  spheroidal  parting  on  a  large  scale  due  to  cooling. 
These  rocks  are  accompanied  by  tuffs  and  breccias  which,  in 
spite  of  subsequent  dynamic  action,  still  show  their  original 
characters.  In  one  case,  on  the  island  of  Gjeitung,  occurs  a 
deposit  of  pumice  bombs  cemented  by  what  is  now  a  chlorite 
schist.' 

In  Sweden  Hogbom  describes  the  general  distribution  of 
post-Archean  (Algonkian)  eruptive  rocks,  many  of  which  bear 
unmistakable  evidence  of  volcanic  character.'  Otto  Norden- 
skjold  assigns  the  beautiful  flow-porphyries  and  amygdaloids  of 
the  Elfdalen  region  to  the  same  horizon,  while  he  concludes  that 
most  of  the  Halleflintas  of  southeastern  Sweden  (Smiland)  are 
surface  lavas.  He  finds  in  them  such  well-developed  fluidal, 
eUtaxitic,  rhyolitic  and  perlitic  structures  that  they  may  be 
regarded  as  old  rhyoHtes  or  devitrified  obsidians.^  The  probably 
much  younger  and  still  glassy  rhyolites  of  the  gneiss  area  of 
Lake  Mien  are  described  by  N.  O.  Hoist.* 

In  Russia  Tschernyschew  describes  from  the  central  Urals, 
many  types  of  eruptive  rocks,  and  among  them  both  acid  and 
basic  volcanics  of  great  antiquity,  accompanied  by  their  agglom- 
erates, breccias  and  tuffs.' 

In  America  the  recognition  of  the  true  character  and  relation- 
ships of  ancient  volcanic  rocks  has  been  greatly  retarded  both 


'Bdmmeloen  og  Kannoen,  pp.  109,  122,  and  403,  1888. 
"Geologiska  Foren.  i  Stock.  Forh.,  Vol.  15,  p.  209,  1893. 
3  Bull.  geol.  See.  Upsala,  Vol.  I,  Nos.  I  and  2, 1893. 
*  Afhandl.  Sverig.  geol.  Undersok.     Ser.  C,  No.  no,  1890. 
SAllgemeine  geologische  Karte  von  Russland,   Bl.  139,  Central  UraU.      Text  4° 
pp.  323  and  333,  1889. 


"Sft-itjS.'^P 


THE  DISTRIBUTION  OF  ANCIENT  VOLCANIC  ROCKS.      9 

by  the  adherents  to  the  so-called  metamorphic  school,  like  Dana, 
Logan,  Rogers,  Lesley  and  Winchell,  who  fail  to  find  among 
the  ancient  foliated  crystallines  anything  beside  altered  sedi- 
ments, but  perhaps  even  more  by  the  influence  of  that  most 
extreme  of  all  Wernerians,  Dr.  T.  Sterry  Hunt.  While  antithet- 
ically opposed  to  the  members  of  the  metamorphic  school  in  his 
notions  of  lithological  character  as  an  index  of  geological  posi- 
tion, Dr.  Hunt  had  in  common  with  them  the  conviction  that  the 
ancient  lavas  and  volcanic  breccias,  tuffs  and  ash-beds  were 
normal  aqueous  deposits.  The  basic  volcanics  of  eastern  North 
America  enter  so  argely  into  his  "  Huronian,"  and  the  acid 
types  so  largely  into  his  "  Arvonian,"  that  his  writings  may  still 
be  used  as  suggestive  of  localities  where  ancient  effusive  rocks 
may  be  sought  for.' 

But  there  have  not  been  wanting  those  among  the  earlier 
American  geologists  who  have  clearly  recognized  the  igneous 
members  of  the  ancient  crystalline  formations,  in  spite  of  their 
disguised  character.  Prominent  among  them  are  E.  Hitchcock, 
Emmons,  Lieber,  Foster  and  Whitney.  Not  only  the  igneous, 
but  the  volcanic  (surface)  character  of  the  Lake  Superior  lavas 
has  been  maintained  by  Pumpelly,'  Wadsworth,3  Irving,*  Van  Hise^ 
and  the  present  writer.*  In  Canada  igneous  rocks  have  always 
been  regarded  abundant  in  the  oldest  formations,  while  the 
volcanic  character  of  some  of  them  has  been  insisted  on  by 
Selwyn  ?  and  mentioned  by  other  members  of  the  Canadian  Geo- 
logical Survey.  A  looseness  of  usage  is,  however,  observable  in 
some  of  these  reports,  where  "  volcanic "  is  made   synonymous . 

'See:  Presidential  Address,  Am.  Assn.  Adv.  Sci.,  1871  ;  Proc.  Am.  Assn.  Adv. 
Sci.,  1876,  p.  211-211;  Azoic  Rocks,  1878;  Am.  Jour.  Science,  May,  1880;  Mineral 
Physiology  and  Physiography,  Chaw  IX.,  1886. 

"Geology  of  Michigan,  Vol.  I,  1873. 

3Bull.Mus.  Comp.  Zool,,  Vol.  7,  p.  iii,  1880. 

« Monograph  v.,  U.  S.  Geological  Survey,  1883. 

5  Bull.  Geol.  Soc.  Am.,  Vol.  4,  p.  435,  1893. 

*Bull.  U.  S.  Geol.  Surv.,  No.  62,  p.  192,  et  seq.,  1890. 

'Report  of  the  Geol.  Survey  of  Canada  for  1877-78.  A,  p.  5.  Trans.  Roy.  Soc. 
of  Canada,  Vol.  i,  p.  10,  1882. 


i 


'4 

I 


lfMft«MMHM%iM 


10 


THE  JOURNAL  OF  GEOLOGY. 


with  "  igneous."  '     In  the  eastern  United  States  Wadsworth  was 
the  first  to  declare  for  the  volcanic   origin  of  the  felsites  and 
tuffs  in  the  Boston  basin  which,  through  the  influence  of  Hunt's 
doctrine  had,  after   Hitchcock's  time,  come  to  be  explained  as 
sediments.     To  Dr.  Wadsworth  also  belongs  the  honor  of  having  , 
been  the  first  geologist  on  this  continent  to  insist  on  the  original 
identity  of  these  old  lavas  and  pyroclastics  with   the  recent  vol- 
canic  rocks  of  the  Cordilleras.'     There  is  little  doubt  that  the 
finely  preserved  ancient  volcanic  material  in  the  eastern  crystalline 
belt  and  elsewhere  will,  when  it  is    adequately  studied,   finally 
bring  to  this  opinion  most  American   geologists.     If  we  as  yet 
know  little  of  the  extent  and  distribution  of  our  ancient  volcan- 
ics,  we  are  at  least  bound  by  no  traditions  to  artificial  and  useless 
age  distinctions,  and  may  freely  follow  the  lead  of  our  English 
colleagues. 

CRITERIA    FOR    THE     RECOGNITION     OF     ANCIENT     VOLCANIC     ROCKS. 

It  is   a   self-evident    proposition  that   the    identification   of 
certain  rocks  as  volcanic  products  is  in  no  way  dependent  upon 
their  present  association  with  a  recognizable  crater  or  volcanic 
mountain.     By  volcanic  rocks  we  understand  igneous  or  pyro- 
clastic  material  which  has  solidified  or  been  deposited  at,  or  very 
near  the  earth's  surface.     It  is  of  little  moment  whether  or  not 
it  was  ever  piled  into  conical  mountains.     That  the  rocks  them- 
selves bear  witness  to  their  origin  and  conditions  of  formation  is 
sufficient.    The  successive  effects  of  erosion  on  the  easily  removed 
.  volcanic  mountains  has  been  so  often  graphically  'iescribeda  that 
no  further  reference  to  the  subject  is  here  necessary.     If   the 
Eocene  or  Triassic  volcanoes  have  so  disappeared  as  to  leave 

"For instance,  Ells  in  his  "Geology  of  the  Eastern  Townships "  (Can.  Kept,  for 
1886,  J.)  speaks  of  pre-Cambrian  rocks  as  "volcanic"  and  "plutonic,"  but  enumerates 
only  granite,  diorite  and  serpentine. 

-Bull.  Mus.  Comp.  Zool.,  Vol.  S,  i879,  P-  277  't  ^'9;  and  Azoic  System,  ib..  Vol.  7, 
1884,  p.  429- 

3  See  DE  LA  Beche:  Geological  Observer,  pp.  526-537.  i8Si-  M.  Neumayr  : 
Erdgesch'ichte,  Vol.  I,  pp.  202-204,  1887.  W.  M.  Davis:  "The  Lost  Volcanoes  of 
Connecticut,"  Popular  Science  Monthly,  Dec,  1891. 


J!i 


•h 


n 


THE  DISTRIBUTION  OF  ANCIENT  VOLCANIC  ROCKS.     1 1 

only  traces  of  their  original  forms,  what  may  we  expect  of  those 
of  Paleozoic  or  Archean  times? 

On  the  other  hand,  the  association  in  dissected  volcanic 
regions  of  the  effusive  rocks  with  correspondingly  abyssal  types 
naturally  suggests  that  volcanoes  may  have  once  surmounted 
many  areas  of  coarsely  granular  ancient  igneous  rocks.  As  this, 
however,  cannot  be  proved,  only  such  regions  are  here  con- 
sidered as  yield  rocks  of  unmistakably  surface  origin. 

Again,  ancient  volcanic  rocks  may  have  been  subjected  to 
metamorphosing  processes  severe  enough  to  have  destroyed 
most  of  their  original  characters.  In  such  cases,  patient  study 
and  a  careful  weighing  of  all  evidence  is  necessary  to  decide 
their  origin,  and  even  that  may  not  avail.  Igneous  rocks  may 
be  so  altered  as  to  be  indistinguishable  from  metamorphosed 
sediments,  but  it  many  cases  where  this  at  first  appears  to  be  the 
fact,  some  decisive  clue  may  be  discovered. 

In  establishing  the  volcanic  nature  of  rocks  occurring  in 
ancient  and  more  or  less  crystalline  terrains,  attention  must  be 
given  to  several  different  sets  of  characters.  The  field  relations 
must  be  carefully  studied  and  the  material  collected  on  the  spot 
and  afterward  studied  in  the  laboratory.  The  criteria  for  decid- 
ing on  their  igneous  and  volcanic  origin  may  be  arranged  as 
follows : 

I.  If  the  rocks  are  igneous,  whether  abyssal  or  surface,  they 
will: 


composition    to    certain   well 


2. 


Conform   in   chemical 
established  types ; 

Show  an  association  of  petrographical  types  which, 
both  chemically  and  mineralogically,  follow  the  laws 
of  consanguinity. 
II.  If  they  are  volcanic  : 

I.  They  may  be  found  in  the  field  to  occur  in  distinct 
sheets,  flows  or  necks  ; 

They  will  have   produced   very  little  or  no  contact 
action  in  the  adjoining  rocks  ; 
They  may  include  irregular  fragments  of  other  rocks. 


2. 


3- 


•I- 

II 


X-i 


II 


-•^Mt^ 


7 


It  THE  JOURNAL  OF  GEOLOGY. 

III.  If  they  are  volcanic  : 

1.  They  may  appear  to  be  striped,  banded,  or  pseudo- 
'•  stratified"  conformably  to  adjoining  sedimentary 
deposits ; 

2.  They  will  probably  be  accompanied  by  fragmental 
(pyroclastic)  material,  which  may  or  may  not  itself 
be  really  stratified.  Such  material  will  vary  greatly 
in  coarseness,  containing  bombs,  agglomerates,  brec- 
cias, tuffs,   sands  and  ashes.     The  characteristics  of 

these  are : 

i)  indiscriminate  mixture  of  all  sizes  and  shapes  of 

fragments ; 

2)  material  of  same  kind  as  the  igneous  rocks; 

3)  cement,  either  finer  fragmental  material  (tuff- 
breccia)  or  lava  (flow-breccia); 

4)  very  angular  shape  of  smallest  fragments  (micro- 
scopic glass  sherds). 

5)  if  ancient  volcanoes  were  on  the  shore-line,  such 
material  may  have  been  immediately  worked  over 
by  water  and  interbedded  with  more  or  less 
normal  aqueous  sediments. 

IV.  Most  important  of  all,  however,  is  the  identification  of 
those  characteristic  structures  known  to  originate  only 
in  glassy,  half-glassy  or  very  fine  grained  porphyritic 
rocks,  solidifying  at  the  surface,  or  in  very  narrow  dykes 
where  solidification  has  been  rapid.  These  will  be  found 
to  be  very  persistent  and  can  usually  be  identified  under 
the  microscope  in  spite  of  devitrification,  alteration,  or 
even  a  considerable  degree  of  dynamometamorphism. 
The  most  common  of  these  structures  are  : 

1.  a  vesicular,  scoriaceous,  pumiceous  or  amygdaloidal 

structure ; 

2.  a  sharply  defined,  small  porphyritic  structure  with  a 
glassy,  half-glassy  or  felsitic  (cryptocrystalline)  base  ; 

3.  a  spherulitic  structure,  due  to  either  large  or  small 
lithopysae,  hollow  spherulites,  or  compact  spherulites. 


THE  DISTRIBUTION  OF  ANCIENT  VOLCANIC  ROCKS.    1 3 

arranged  either  irregularly,  or  in  more  or  less  discon- 
tinuous bands  or  layers ; 

4.  a  flow  structure,  produced  either  by  the  elongation  of 
vesicles  or  the  parallel  arrangement  of  constituents 
or  crystallites.  It  may  also  be  produced  by  the 
interlacing  of  different  colored  magmas  (eutaxitic 
structure) ;  ^ 

5.  corroded  phenocrysts,  quartz  with  embayments,  or 
skeleton  crystals  due  to  rapid  and  imperfect  growth ; 

6.  microscopic  spherulites,  globulites,  trichites,  crystal- 
lites, real  or  devitnfied  glass  inclusions,  quartz  with 
orientated  siliceous  aureoles,  axiolites,  etc.; 

7.  perlitic  structure,  wholly  or  partly  devitrified. 
Although  some  of  these  structures  may  occasionally  occur  in 

dykes  or  other  igneous  rocks  which  have  rapidly  solidified  beneath 
the  surface,  they  are  nevertheless  so  essentially  characteristic  of 
effusive  lavas,  that,  in  lack  of  any  evidence  to  the  contrary,  they 
may  be  regarded  as  fairly  safe  guides  in  establishing  the  effusive 
nature  of  rocks.  This  evidence  is  beyond  doubt,  if  such  rocks 
are  accompanied,  as  they  generally  are,  by  ash  material. 

While  a  single  one  of  these  characteristics  may  not  be  suffi- 
cient to  Identify  a  volcanic  occurrence,  many,  if  not  all  of  them, 
will  be  found  to  occur  together,  and  only  in  rare  instances  will 
it  be  found  that  some  of  them,  at  lea'st,  have  not  survived  the 
vicissitudes  of  metamorphism.  That  many  regions  in  the  ancient 
crystalline  belt  of  the  Appalachian  system  exhibit  most  of  them 
in  great  perfection  is  now  well  known.  It  is  only  a  misinterpre- 
tation of  these  characteristic  features  of  volcanic  rocks,  due  to 
a  lack  of  acquaintance  on  the  part  of  observers  with  their  recent 
analogues,  that  has  prevented  their  recognition  long  ago.  Thus, 
by  those  who  have  heretofore  described  these  rocks  as  sedi- 
ments, both  secondary  cleavage,  and  the  banding  due  to  flow  or 
parallel  spherulitic  layers  have  been  mistaken  for  stratification ; 
spherulites  have  been  erroneously  regarded  as  concretions ;  and 
the  accompanying  pyroclastics,  as  normal  conglomerates  or 
slates. 


if 


11 


M 


THE  JOURNAL  OF  GEOLOGY. 


It  is  the  purpose  of  the  writer  in  the  present  paper  to  main- 
tain that  in  the  great  crystalline  belt  of  eastern  North  America,  large 
areas  of  volcanic  rocks  occur,  and  that  these,  in  spite  of  their  great 
age,  are  in  all  respects  the  same  as  modern  volcanic  materials,  save 
for  alterations  subsequent  to  their  original  formation — among  which 
alteratiom  devitrification  lias  been  one  of  the  most  important.^ 

DISTRIBUTION    OF    VOLCANIC    AREAS    ALONG    EASTERN    NORTH 

AMERICA. 

I  shall  now  proceed  to  summarize  the  present  state  of  our 
knowledge  of  these  volcanic  areas,  as  far  as  they  belong  to  the 
Eastern  or  Appalachian  crystalline  belt,  omitting  all  reference 
to  the  central  Canadian,  Lake  Superior,  Missouri,  or  other  more 
western  regions  of  similar  nature.  In  this  review  I  shall  com- 
mence with  Newfoundland  and  follow  them  southwest,  parallel 
to  the  coast. 

Eastern  Canada. — In  a  recent  comparison  between  the  Eozoic 
and  Paleozoic  rocks  of  eastern  America  and  western  Europe, 
Sir  William  Dawson  says  that  the  Huronian  was  evidently  a 
coarse  marginal  deposit,  accompanied  by  abundant  volcanic  out- 
breaks, similar  to  those  which  occurred  about  the  same  time  in 
Wales.  He  is  also  confident  that  many  of  the  bedded  Huronian 
rocks  are  really  of  volcanic  origin,  being  ashes  in  an  altered  state." 
In  the  same  paper  he  mentions  volcanic  rocks,  both  lavas  and  pyro- 
clastics,  as  abundant  in  the  Ordivician  and  Silurian  formations 
of  eastern  Canada. 

The  reports  of  the  Canadian  and  Newfoundland  surveys 
abound  in  references  to  rocks  of  a  volcanic  character  in  the 
early  Paleozoic  and  pre- Paleozoic  horizons.  These  references 
are,  however,  always  purely  those  of  a  field-geologist  engaged 
in  a  rapid  reconnaissance.  The  frequent  use  of  such  field  terms 
as  felsite,  porphyry,  trap,  amygdaloid,  agglomerate,  breccia  and 
ash    suggest  a  vast  development  of  contemporaneous  volcanic 

'  On  the  nomenclature  of  these  ancient  and  devitrified  lavas,  see  Miss  Florence 
Bascom's  paper,  this  Journal,  Vol.  I.,  No.  8,  p.  825,  Nov.-Dec.  1893. 

»  Quart.  Jour.  Geol.  Soc,  Vol.  44,  p.  801,  1888. 


^% 


■ii- 


THE  DISTRIBUTION  OF  ANCIENT  VOLCANIC  ROCKS.     I  5 

materials,  but  thus  far  no  petrographcr  has  attempted  to  study 
systematically  either  the  field  or  microscopical  relations  of  any 
area  of  these  interesting  rocks.  A  very  broad  and  interesting 
field  is  thus  seen  to  be  awaiting  investigation  in  Newfoundland, 
Gasp^,  New  Brunswick,  Nova  Scotia  and  the  Eastern  Town- 
ships. 

Professor  J.  B.  Jukes,  in  his  "Geology  of  Newfoundland," 
describes  old  lava  flows  and  accompanying  pyroclastic  deposits 
as  very  abundant,  especially  on  the  peninsula  of  Avalon,  which 
forms  the  eastern  part  of  the  island.'  His  observations  are  con- 
firmed by  the  later  reports  of  Murray  and  Howley,  who  agree 
that  the  western  part  of  this  peninsula  was  the  scene  of  extraor- 
dinary volcanic  activity  in  very  early  times." 

In  his  three  reports  on  the  eastern  portion  of  Cape  Breton, 
Fletcher  describes  the  Ste.  Anne,  Boisdale,  Coxheath,  East  Bay 
and  Mira  Hills,  as  composed  largely  of  ancient  (pre-Cambrian) 
volcanic  rocks,  an.ong  which  felsites  of  all  colors,  felsite-por- 
phyries,  felsite  breccias  and  amygdaloids  abound.^  Similar 
rocks  appear  also  to  extend  up  into,  and  to  form  an  important 
part  of  the  Cambrian,  Silurian  and  Devonian  formations.  In  a 
later  report  on  the  northern  part  of  Cape  Breton,  Fletcher  ♦  finds 
that  the  greater  part  of  the  northern  peninsula  is  also  composed 
of  "  felsites,"  but  the  petrographical  distinctions  of  both  Fletcher 
and  Gilpin  ^  are  so  indefinite  that  a  variety  of  coarsely  crystal- 
line rocks  seem  to  be  embraced  in  this  general  designation.  In 
describing  the  Mira  "felsites,"  Fletcher  mentions  those  of  Blue 
Mountain  and  Gull  Cape,  near  Louisburg,  as  being  "globular," 
or  "concretionary,"  (coarsely  spherulitic?)  often  presenting 
"single  or  united  spheroids,  the   concentric  layers  of  which  may 

'  Excursions  in  and  about  Newfoundland  in  1839  and  1840,  2  vols.,  1843.  Geol- 
ogy, Vol.  2,  pp.  245-341. 

'Reports  of  the  Geological  Survey  of  Newfoundland  for  1868-1881. 

3  Reports  of  the  Geol.  Survey  of  Canada,  1875-76,  pp.  369-418;  ib.,  1876-77, 
pp.  402-456;  ib.  1877-78,  pp.  1-32,  F. 

Mb.,  1882-83-84,  pp.  1-98  H.  ,  . 

s  Quart.  Jour.  Geol.  Soc,  Vol.  42,  p.  515,  1886. 


ii 


—if0r 


i6 


THE  JOURNAL  OF  GEOLOGY. 


be  removed  like  the  coats  of  an  onion."  He  also  speaks  of 
them  as  "coarsely  brecciated"  and  "vesicular."  A  point  of 
some  interest  is  Fletcher's  conclusion  that  "both  felsite  and 
syenitic  strata  are  intimately  associated  as  part  of  the  same 
group  of  crystalline  rocks,  differing,  not  so  much  in  composi- 
tion as  in  the  degree  of  crystallization  they  have  been  subjected 
to"  («V).'  In  greatly  eroded  regions  we  should  expect  to  find 
surface  volcanic  rocks  associated  with  their  coarser  abyssal 
equivalents. 

In  Nova  Scotia  proper  the  best  known  area  of  ancient  vol- 
canic rocks  is  in  the  northeastern  corner  of  the  province,  near 
Arisaig,  in  Antigonish  county.  These  were  considered  by  Sir 
William  Dawson  in  1850  as  "metamorphic."'  In  1864,  Dr. 
Honeyman  described  them  as  vesicular  traps,  amygdaloids  and 
porphyries,  associated  with  tufa  and  tufaceous  conglomerate.^ 
In  his  first  report  on  eastern  Nova  Scotia,  Fletcher  describes 
variegated,  vesicular  and  amygdaloidal  "felsites"  and  "frag- 
mentary felsites,"  like  those  of  Coxheath  and  Louisburg,  asso- 
ciated with  "syenite"  (hornblende  granite)  and  diorite.*  These 
rocks  are  regarded  as  pre-Cambrian,  and  are  particularly  devel- 
oped at  Arichat,  Cape  Porcupine  on  the  Straits  of  Canso,  and  in 
the  Sporting,  North  and  Craignish  mountains.  In  the  North 
Mountains  the  felsites  are  said  to  pass  gradually  into  syenite 
(1.  c.  p.  14).  The  gradual  blending  of  the  felsite  and  overlying 
George  River  limestone  is  attributed  to  "common  metamorph- 
ism,"  rather  than  "to  contemporaneous  volcanic  origin  or  sub- 
sequent intrusion"  (1.  c.  p.  17).  Nevertheless,  at  Cape  Porcu- 
pine the  felsite  is  regarded  as  possibly  an  igneous  rock,  since 
"the  apparent  lines  of  bedding  are  like  those  of  a  furnace  slag" 
(1.  c.  p.  25).  In  the  subsequent  report  of  the  extension  of  his 
explorations  southward  and  westward  in  Nova  Scotia,  Fletcher 
admits  the  volcanic  origin  of  the  felsitic  rocks  of  Arisaig,  Doc- 

' Quoted  by  Gilpin  :  Quart.  Jour.  Geol.  See,  Vol.  42,  p.  lib. 

"Quart.  Jour.  Geol.  Soc,  Vol.  6,  p.  347,  1850. 

3  lb.,  Vol.  20,  p.  333,  1864. 

«  Report  of  the  Geol.  Sun/ey  of  Canada,  1879-80,  F. 


TJfE  niSTRlRUTION  OF  ANCIENT  VOLCAX/C  ROCKS.    1/ 


tor's  Brook,  Georpeville,  Blue  Mountain  and  Kast  River  of  St. 
Mary's.  These  arc  quite  like  the  Cape  Breton  and  Cape  I'orcu- 
pine  rocks,  and  carry  copper,  as  they  do  in  South  Mountain,  Pa., 
and  on  Lake  Superior.  He  gives  the  age  of  these  eruptions  as 
probably  pre-Cambrian,  although  at  Arisaig  they  may  be  of  any 
age  older  than  Medina.  Similar  volcanic  eruptions  occur  in  all 
strata  up  to  the  base  of  the  Carboniferous.'  In  his  last  report 
covering  Pictou  and  Colchester  counties,  the  same  author 
describes  Cambro-Silurian  porphyries,  agglomerates,  fragmental 
felsites,  breccias  and  amygdaloids  from  Moose  and  Sutherland 
rivew.  A  dyke-like  mass  of  volcanic  breccia  occurs  on  Sam 
Cameron's  brook.  Similar  volcanic  products  arc  also  very 
apparent  in  the  Devonian  of  these  two  counties,  among  the  most 
interesting  of  which  are  the  syenitic  granites  overlaid  by  thick 
volcanic  deposits  at  the  east  end  of  the  Cobequid  Hills,  as 
described  by  Dawson.'  The  well-known  traps  of  northwestern 
Nova  Scotia,  along  the  Bay  of  Fundy,  which  furnish  the  beauti- 
ful zeolites  and   other  minerals,  are  of  Triassic  age. 

In  New  Brunswick  and  the  Gaspe  Peninsula,  old  volcanic 
rocks,  like  those  of  Newfoundland  and  Nova  Scotia,  are  exten- 
sively developed.  Ells  and  Low  mention  amygdaloidal  traps  and 
porphyries  cutting  various  strata  of  Gaspe,  up  to  and  including 
the  Devonian.3  Felsitic  rocks,  similar  to  those  which  are  better 
known  further  to  the  south,  are  rather  vaguely  mentioned  by 
Robb  in  northern  New  Brunswick.*  Ells,  in  his  report  on  the 
same  region  in  1879-80,  clearly  describes  as  volcanic  both  acid 
and  basic  rocks.  A  vast  area  of  felsite,  petrosilex,  porphyry 
and  breccia,  like  that  near  St.  Johns,  is  developed  in  the  upper 
Nipisiguet  river  and  lake  Nictor.  Another  like  it  extends 
from  the  upper  Upsalquitch  river  along  Jacket  river  to  the 
bay  of  Chaleur,  while  great  masses  of  basic  volcanics    (amyg- 

'Ib.,  1886,  p. 

•Acadian  Geology,  1878,  suppl.,  p.  79. 

Report  of  the  Geol.  Survey  of  Canada,  new  ser.,  Vol.  5,  1890-qi,  P.  pp.  147-166. 
»lb.,  1882-83-84,  E,  and  F. 
*lb.,  1870-71,  p.  245. 


.H 


i8 


THE  JOURNAL  OF  GEOLOGY. 


daloids,  aphanitcs,  etc.)  occur  around  the  head  of  the   Bay  ol 
Chaleur  and  Dalhousie,  as  well  as  on  the  upper  Upsalquitch  and 
Klni  Tree  rivers.     Many  of  these  rocks  are  pre-Cambrian,  while 
others  cut  the  Silurian  strata.'     Great  sheets  of  contemporane- 
ous trap  arc  also  found  by  Ells  in  the  Silurian,  and   to  a  very 
small  extent  in  the  Devonian,  along  .he  north  shore  of  the  Bay 
of  Chaleur.     Bailey  explored  parts  of  northern  and  western  New 
Brunswick,  especially  in  Carolton,  York  and  Victoria  counties, 
and  found  porphyries,  felsites  and  amygdaloids,  intrusive  in  the 
Silurian  and  older  formations  in    Canterbury,  Woodstock  and 
Kent  townships,   near  the  St.  Johns   river.*     Still   later  Bailey 
and  Mclnnes  continued  similar  explorations,  and  found  signs  of 
intense  volcanic  action  in  the  Niagara  limestone  at  Pointe  aux 
Trembles,  and  a  great  development  of  acid  and  basic  surface 
rocks  near  the  Aroostook  river  and  at  Presqu'ile  and  Haystack 
mountain    in   Maine.'     The   same    is  true   near  Tobique   lake, 
farther  to  the  northeast. 

As  early  as  1839,  Gesner  describes  the  volcanic  rocks  along 
the  Bay  of  Fundy,  in  southern  New  Brunswick,  as  belonging 
to  several  distinct  horizons."  In  1865,  Bailey,  Matthew  and 
Hartt  distinguished  two  groups  mainly  of  volcanic  origin,  to  one 
of  which,  the  "Coldbrook,"  they  assigned  a  Huronian,  and  to 
the  other,  the  "  Bloomsbury,"  a  Devonian  age.*  In  1872, 
Bailey  and  Matthew,  after  a  season's  field-work  with  Dr.  T. 
Sterry  Hunt,  united  the  Coldbrook  and  Bloomsbury  groups  on 
purely  lithological  grounds,  and  for  the  same  reason  joined  with 
them  two  other  volcanic  series — the  Coastal  and  Kingston 
groups— exposed  at  other  localities  in  southern  New  Bruns- 
wick.* The  petrographical  characters  of  these  rocks  were  those 
regarded  by  Hunt  as  sufficient  demonstration  oi  Huronian  age. 
The  acceptance  of  this  fallacious  principle  exercised  a  distinctly 

•  lb.,  1879-80,  pp.  35  to  42. 

«Ib.,  2882-83-84,  G.  pp.  15  and  20;  ib.,  1885,  G.  pp.  22  and  28. 

3  lb.,  1886,  N.  pp.  14-1S ;  and  ib.,  1887-88,  M.  pp.  32  and  47. 

4  First  Report  on  the  Geological  Survey  of  the  Province  of  New  Brunswick,  by 
Abraham  Gesner.    87  pp.     1839. 

5  Observations  on  the  Geology  of  Southern  New  Brunswick.     1865. 
«  Report  of  the  Geol.  Survey  of  Canada,  1870-71,  pp.  57-I33' 


1 


THE  DISTRinUTlON  OF  ANCIENT  VOLCANIC  ROCKS.     1 9 

retarding  effect  on  the  deciphering  of  New  Brunswick  geology. 
Numerous  occurrences  of  fclsite,  porphyries  and  aniygdaloids 
were  described  between  Muscpiosli  Harbor  and  Loch  Lomond, 
near  the  city  of  St.  Johns,  and  along  the  line  between  Kings 
and  Queens  counties  (Coldbrook  and  Bloomsbury  groups). 
Similar  rocks  were  traced  from  L'Etang  ILirbor,  near  I'assama- 
quoddy  Bay,  along  the  edge  of  the  Bay  of  Fundy  to  Shepody, 
in  Albert  Coiinty  (Coastal  group);  and  finally,  a  belt  of  ana- 
logous composition  was  described  between  the  Long  Reach  of 
the  St.  Jol  MS  river  and  Mace's  bay  (Kingston  group).  These 
rocks  were  it  this  time,  however,  on  account  of  Hunt's  influ- 
ence, united  with  their  associated  sediments,  and  nothing  is  said 
about  their  volcanic  character.  These  authors  were  forced  to 
regard  similar  rocks  on  the  shores  of  Passamaquoddy  bay  as 
Silurian,  because  of  associated  fossils,  in  spite  of  their  litholog- 
ical  identity  with  the  "  Huronian."  These  they  called  the  Mas- 
carene  scries,' 

Four  years  later  the  same  authors  united  the  Kingston  and 
Mascarene  groups  and  regarded  both  as  upper  Silurian."  In  a 
report  of  the  pre-Silurian  rocks  of  Albert,  eastern  Kings,  and 
St.  Johns  counties.  Ells  gives  some  clear  statements  relative  to 
the  volcanic  rocks  of  southern  New  Brunswick.     He  says  : 

"  In  their  lithological  aspect,  the  rocks  forming  the  southern  metamorphic 
belt  present  great  diversity.  Their  general  character  is  of  two  kinds— altered 
sedimentary  and  volcanic.  *  *  *  In  the  latter  we  include  the  great  mass 
of  petrosiliceous  rocks,  so  called,  with  breccias  and  other  ash  rocks,  which 
in  places  show  bedding,  but  this  is  often  so  obscurely  marked  as  to  be  exceed- 
ingly doubtful.  ♦  *  *  Near  the  contact  of  the  volcanic  and  sedimentary 
rocks  we  find  an  extraordinary  development  of  generally  coarsely  crystalline 
diorites  and  syenites,  which  would  seem  to  form  the  basal  portion  of  the  vol- 
canic part  of  the  series."' 

A  report  on  the  same  rocks  was  published  at  the  same  time 
by  Bailey,  who  divides  them  into  a  feldspathic,  syenetic  and 
gneissic  group,  including  limestones,  serpentines,  and  dolomites 

'lb.,  pp.  144-158. 

Mb.,  1874-7S,  pp.  85-89. 

3lb.,  i877-78,D.  p.  3. 


THE  JOURNAL  OF  GEOLOGY. 

(Laurcntian);  a  felsitc-pctrosilcx  group  (Lower  Huronian  or 
Coldbrook;;  and  a  schistose,  chloritic  micaceous  group  (Upper 
Huronian  or  Coastal).'  The  results  of  all  their  work  on  the 
rocks  of  southern  New  Brunswick  is  summarized  by  Bailey, 
Matthew  and  Ells,  with  a  general  geological  map  in  three 
sheets." 

That  portion  of  the  Province  of  Quebec  lying  south  and 
east  of  the  St.  Lawrence  is  called  the  Eastern  Townships.  We 
have  already  considered  that  portion  of  it  composing  the  Gasp* 
peninsula.  The  portion  lying  west  of  Maine  and  north  of  New 
Hampshire  and  Vermont  was  supposed  by  Logan  to  be  wholly 
occupied  by  rocks  of  the  Quebec  Group.  In  1879,  Dr.  Selwyn 
divided  the  rocks  of  this  zone  into  three  groups,  which  he 
defined  as  lower  Silurian;  volcanic  (probably  lower  Cambrian); 
and  crystalline  (probably  Huronian).  The  lower  of  these  divis- 
ions forms  an  anticlinal  axis  extending  from  Lake  Memphrema- 
gog  to  L'Islet  County,  150  miles.  It  contains  a  great  variety 
of  altered  sedimentary  beds,  associated  with  "diorites,  doler- 
ites,  serpentines,  amygdaloids,  and  volcanic  agglomerates," 
regarded  by  Hunt  as  altered  sedimentaries.  The  second  divis- 
ion, said  to  be  intimately  related  to  the  last,  is  largely  composed 
"  especially  on  the  southeastern  side  of  the  axis,  of  altered  volcanic  products 
both  intrusive  and  interstratified,  the  latter  being  clearly  of  contemporaneous 
origin  with  the  associated  sandstones  and  slates." 

These  rocks  are  designated  as 
"dioritic,   epidotic,   and  serpentinous  breccias  and  agglomerates;  diorites, 
dolerites  and  amygdaloids   holding   copper  ore;    serpentines,   felsites  and 
some  fine  grained  granitic  and  gneissic  rocks." 

They  are  especially  developed  along  the  contact  of  the  last- 
mentioned  group,  of  which  they  "may  be  merely  the  upward 
extension."  3  In  a  later  paper  on  the  Quebec  Group,  Dr.  Sel- 
wyn considers  these  volcanic  rocks  thoroughly  from  the  English 
point  of  view.     He  says  : 

•  lb.,  DD.  p.  2. 

» lb.,  1878-79,  D.  p.  26. 

3  lb.,  1877-78,  A.  pp.  5-9. 


"^ 


THE  DISTRIIiVriON  OF  ANCIENT  VOLCANIC  ROCK'S.    21 

"  I  would  alsi>  Buhmit  that  neither  a  RchiiitiiRe  nor  a  bedded  utructure  can  he 
accepted  as  proof  of  a  non-i>(neouH  or  volcanic  «)rif(in,  and  that  a  once  mas- 
sive lava-flow,  whether  auKitic  or  feldspathic,  is  as  likely,  through  presiure 
and  metaniorphism,  to  assume  a  schistose  structure  as  are  ordinary  sedi- 
mentary slriJta.  It  is,  I  am  aware,  not  in  accordance  with  generally  receiveil 
ideas  on  the  nature  of  ancient  igneous  rocks  to  supjiose  they  can  be  schistose 
and  stratified,  especially  so  in  America,  where  volcanic  agency  in  the  earlier 
geological  periods  has  been  almost  entirely  ignored,  and  all  those  rocks 
which  by  their  microscopic  characters  and  chemical  conifiosition,  and  by 
their  geological  associations  and  relations,  point  to  volcanic  agency  as  the 
cause  of  their  formation,  have  been  said  to  be  '  not  if^'tteoiis,  bitf  tnelumorfihic 
in  origin;  a  description  which,  it  seems  to  me,  is  decidedly  self-cimtradic- 
tory."  • 

Sclwyn  later  again  maintained  his  volcanic  group,  and  pub- 
lished microscopic  descriptions  of  some  of  its  rocks  (cjuartz- 
porphyry  and  porphyrite)  by  Adams.»  Little  or  nothing  is  added 
to  our  knowledge  of  the  strictly  volcanic  rocks  by  the  two  sub- 
sequent reports  on  the  geology  of  the  Eastern  Townships  by 
Ells.3 

The  recognition  of  ancient  volcanic  rocks  in  the  United 
States  is  far  behind  that  which  prevails  in  Canada.  This,  as 
has  already  been  pointed  out,  is  due  to  the  influence  of  so-called 
"metamorphic"  ideas,  or  more  properly  to  the  Wernerian  doc- 
trine, that  every  rock  showing  any  foliated  or  parallel  structure 
is  sedimentary. 

Nexv  England. — Very  little  definite  information  can  be  gath- 
ered from  the  earlier  reports  on  the  geology  of  Maine,  by  Jack- 
son and  C.  H.  Hitchcock,  regarding  the  old  volcanic  deposits. 
Jackson  frequently  uses  such  petrographical  terms  as  "amygda- 
loidal  trap,  ribbon  jasper,  clinkstone  porphyry,  and  breccia  com- 
posed of  an  infinity  of  fragments  of  jasper,"  in  describing  the 
rocks  near  Eastport  and  Machiasport,  on  the  Maine  coast.  He 
regarded  the  basic  rocks  (trap)  as  eruptive,  but  the  "jasper"  as 
semifused  sediments  whose  lines  of  stratification  weie  still  pre- 

'  Trans.  Roy.  See.  Canada,  Vol.  i,  p.  lo,  1882. 

"  Report  of  the  Geol.  Survey  of  Canada,  1880-82,  A.  p.  2  and  pp.  10-14. 

3  lb.,  1886,  J.,  and  ib.,  1887-88,  K. 


-.or 


22 


THE  JOURNAL  OF  GEOLOGY. 


served.'  His  descriptions  are,  however,  very  suggestive,  espe- 
cially in  light  of  the  truly  volcanic  rocks  which  have  been 
recently  discovered  in  the  older  strata  of  Maine.  C.  H.  Hitch- 
cock, in  his  Maine  reports,  regards  the  acid  volcanic  rocks  near 
Machiasport  as  altered  slates,  and  mentions  extensive  areas  of 
similar  rocks  on  Mooseh<  ad,  Portage,  Long,  and  Chamberlain 
lakes,  as  well  as  along  the  Aroostook  and  Penobscot  rivers,  in  the 
interior  of  the  state.*  Goodale  gives  four  patches  of  analogous 
"siliceous  slates"  in  York  county,  and  five  in  Oxford  county, 
and  J.  H.  Huntington  describes  the  summit  of  the  diorite  south- 
east of  Kennebago  lake,  in  western  Maine,  as  composed  of  com- 
pact felsite,  which  he  regards  as  an  eruptive  rock.3  The  first 
definite  descriptions  of  ancient  volcanic  rocks  in  Maine  was 
given  by  Professor  Shaler,  who  examined  the  regions  about 
Eastport  and  Mount  Desert.  Near  Eastport,  and  especially  on 
McMaster's  island,  three  types  of  volcanic  material  are  largely 
developed :  i )  detrital  accumulations  which  have  fallen  through 
the  air;  2)  true  lava  flows;  3)  dykes.  They  seem  to  belong  to 
various  horizons  of  Silurian  age.*  A  similar  series  of  interstrati- 
fied  volcanic  breccias,  lava  flows  and  ash  beds  are  described  as 
forming  a  large  part  of  Mt.  Desert  island  south  of  Southwest 
Harbor,  and  the  Cranberry  Isles.' 

The  writer  has  had  the  opportunity  to  personally  examine 
the  volcanic  rocks  of  the  Mt.  Desert  region,  and  he  is  indebted 
to  Professor  W.  S.  Bayley  of  Waterville,  Me.,  for  specimens  and 
slides  of  the  beautiful  lavas  of  Vinal  Haven,  and  to  Mr.  E.  B. 
Mathews  for  notes  and  specim.ens  of  similar  rocks  from  Mt. 
Kineo  on  Moosehead  Lake. 

Along  the  shores  of  Cranberry  Island  occur  hard  jaspery 
felsites,  often  porphyritic,  and  exhibiting  such  characteristic 
features  of  glassy  rocks  as  spherulites,  single  and  in  bands,  flow- 

'  First  Report  on  the  Geology  of  the  State  of  Maine,  1837,  p.  12  and  pp.  36-42. 

'Geological  Report,  1 86 1,  p.  190,  and  p. 432;  also  ib.,  1863.  p.  330. 

sPrpc.  Am.  Assn.  Adv.  Sci.,  Vol.  26,  p.  286,  1877. 

♦Am.  Jour,  of  Science  (3d  ser.).  Vol.  32,  pp.  40-43,  1886. 

sEighth  Ann.  Report  U.  S.  Geol.  Survey,  pp.  1037,  1043,  1054.     1889. 


PHm 


THE  DISTRIBUTION  OF  ANCIENT  VOLCANIC  ROCKS.    23 

structure,  etc.,  in  great  perfection,  although  all  trace  of  the 
original  glass  has  long  since  disappeared.  The  rocks  collected 
by  Professor  Bayley  on  the  north  side  of  Vinal  Haven  and  on 
the  opposite  shore  west  of  North  Haven  are,  according  to  his 
field  observations,  all  surface  flows  or  tuffs.  Of  the  nine  speci- 
mens kindly  submitted  to  me  for  examination  by  Professor 
Bayley,  one  is  a  medium  grained  microgranite  and  all  the  others 


tiu.  I. 

Fig.  I.     Devitrified  glass-breccia  from  north  side  of  Vinal  Haven,  Penobscot  Bay, 
Me.     Magnified  six  times. 

are  devitrified  glassy  rocks,  which  were  once  either  obsidians, 
glass  breccias,  or  tuffs.  No.  94  is  a  banded  flow-felsite,  a  devit- 
rified glass  with  narrow  chains  of  spherulites.  No.  100  is  a 
devitrified  obsidian  containing  delicate  flow-lines  produced  by 
trichites,  some  zircon  crystals,  and  spherulitic  bands  in  which 
epidote  has  been  secondarily  produced.  No.  1 26  is  a  pale  gray 
felsite  containing  large  round  nodules  which  may  be  spherulites. 
Under  the  microscope  it  shows  a  pronounced  perlitic  structure. 
These  rocks  contain  spherulitic  structures  which  are  not  devitri- 
fication products  but  original,  if  we  may  judge  from  their  abso- 
lute identity  with  similar  structures  in  the  glassy  rocks  from 
Obsidian  Cliff.     The  other  five  specimens  are  fine  grained  vol- 


THE  JOURNAL  OF  GEOLOGY. 

canic  ashes,  most  of  them  composed  of  very  sharply  angular 
fragments  of  devitrified  glass  or  pumice  with  beautiful  flow 
structures.  The  delicate  detail  produced  by  trichites  in  one  of 
these  is  rather  roughly  represented  in  Fig.  i.  It  is  not  unlike 
the  devitrified  glass-breccia  described  by  the  writer  from  Onap- 
ing  river  in  the  Sudbury  district.' 

The  specimens  collected  by  Mr.  Mathews  at  Mount  Kineo 
on  Moosehead  Lake,  and  kindly  loaned  me  for  examination,  are 
typical  quartz-porphyries  or  keratophyres,  some  of  which  exhibit 
such  perfect  and  delicate  flow-lines  that  they  can  be  regarded 
only  as  devitrified  glassy  lavas. 

In  New  Hampshire  felsites  and  quartz-porphyries  abound. 
They  were  regarded  as  eruptive  by  Hitchcock  and  by  Hawes 
when  they  occur  in  dykes,  although  the  latter  regarded  many  of 
them,  especially  when  interstratified,  as  sediments  fused  in  situ." 
There  are  as  yet  no  published  descriptions  which  make  it  reason- 
ably certain  that  truly  volcanic,  as  contrasted  with  abyssal 
igneous  rocks,  occur  within  this  state. 

The  important  development  of  ancient  volcanic  rocks  in 
eastern  Massachusetts,  in  the  neighborhood  of  Boston,  has  been 
more  discussed  than  any  other  similar  region  on  this  continent. 
An  excellent  resume  of  the  development  of  opinion  regarding 
these  rocks  has  been  given  by  Whitney  and  Wadsworth.»  E. 
Hitchcock  held  correct  views  as  to  the  igneous  character  of  all 
the  massive  rocks,  although  he  regarded  the  amygdaloids  and 
some  of  the  apparently  stratified  felsites  as  altered  sediments. 
Later  the  influence  of  Hunt  created  a  general  impression  that  the 
greater  part  of  these  rocks — even  the  granites — were  of  sedi- 
mentary origin.  Wadsworth  was  the  first  to  successfully  combat 
this  idea,  and  to  show  that  not  only  were  the  coarsest  massive 
rocks  igneous  masses,  but  even  the  finer  jaspery  felsites  and  their 

■  Bull.  Geol.  Soc.  Am.,  Vol.  2,  p.  138,  1891. 
Report  of  the  Geol.  Survey  of  Canada,  1890-91,  F.  p.  75. 

«  See  Geology  of  New  Hampshire,  Vol.  2,  p.  260,  and  Vol.  3,  part  IV.,  Mineralogy 
and  Lithology,  p.  i?'.  '878. 

3  The  Azoic  System,  pp.  398-440,  1884.  1 


THE  DISTRIBUTION  OF  ANCIENT  VOLCANIC  ROCKS.    25 

accompanying  fragmental  materials  were  the  products  of  ancient 
volcanic  action.  He  maintained  that  the  felsites  of  Marble 
Head  were  merely  altered  rhyolites  which  had  once  been  quite 
like  those  of  the  western  Cordilleras  ;  and  their  banding  was  flow- 
structure  ;  and  that  they  were  accompanied  by  ash  beds  which 
he  cz!l\&A  porodites}  Two  years  later  the  detailed  work  of  Diller 
and  Benton  established  the  volcanic  character  of  the  felsites  of 
Mcdford,  Melrose,  Maiden,  Sangus,  Wakefield  and  Lynn,  and  of 
the  amygdaloid  of  Brighton.' 

Other  areas  of  similar  rocks  occur  near  Newburyport,  and 
also  to  the  south  of  Boston  at  Needham,  Dedham,  Milton,  Blue 
Hill,  Hingham,  Nantasket  and  Manomet,3  but  these  have  not  as 
yet  been  so  carefully  examined  as  those  farther  north,  although 
Crosby,  in  his  recent  "  Geology  of  Hingham,"  classes  the  mela- 
phyre.  porphyrite,  and  felsite  of  Nantasket  and  Hingham  as 
effusive  or  volcanic  rocks,  and  describes  the  latter  as  '•  undoubt- 
edly an  ancient,  devitrified  obsidian."* 

The  Middle  Atlantic  States. — In  New  York  state  there  are, 
as  far  as  the  writer  is  aware,  no  remains  of  igneous  rock  which 
have  solidified  at  the  surface.     Nevertheless,  the  isolated  and 

'  The  Classification  of  Rocks.  Bull.  Mus.  Comp.  Zool.,  Harvard  Coll.,  Vol.  5,  p. 
282,  1879.  It  is  worthy  of  note,  in  view  of  all  the  erroneous  ideas  1  'at  have  prevailed 
regarding  the  Boston  felsites,  that  as  early  as  1822.  Dr.  Thomas  Cooper,  President  of 
the  College  of  South  Carolina,  in  an  article  on  "Volcanoes  and  Volcanic  Substances" 
says  :  "  No  person  accustomed  to  volcanic  specimens  can  look  at  the  porphyries  from 
the  neighborhood  of  Boston,  in  my  possession,  and  doubt  of  their  volcanic  origin." 
(Am.  Jour,  of  Science,  1st  ser..  Vol.  4,  p.  239). 

""The  Felsites  and  Their  Associated  Rocks  North  of  Boston,"  by  J.  S.  Diller, 
Bull.  Mus.  Comp.  Zool.,  Vol.  VII.,  p.  165,  1881;  and  "  The  Amygdaloidal  Melaphyreof 
Brighton,  Mass.,"  by  E.  R.  Benton,  Ph.D.,  Proc.  Bost.  Soc.  Nat.  Hist.,  Vol.  20,  pp. 
416-426,  1880.  The  writer  is  indebted  to  Mr.  Diller  for  the  privilege  of  examining 
his  collection  of  slides  of  the  Boston  rocks  which  are  in  all  essential  respects  identical 
with  those  from  the  coast  of  Maine,  from  South  Mountain  and  North  Carolina. 

3  E.  Hitchcock  :  Final  Report  on  the  Geology  of  Massachusetts,  Vol.  i,  p.  150, 
1841  i  W.  O.  Crosby  :  Geology  of  Eastern  Massachusetts,  pp.  79-95.  1880. 

«  Proc.  Bost.  Soc.  Nat.  Hist.,  Vol.  25,  p.  502,  1892.  See  also  by  the  same  author : 
The  Lowell  Free  T.ectures  on  the  Physical  History  of  the  Boston  Basin,  1889  ;  and  the 
Geology  of  the  Boston  Basin,  Vol.  I,  Part  i.  Occasional  Papers  of  the  Boston  Soc. 
Nat.  Hist.,  IV.,  1893. 


26 


THE  JOURNAL  OF  GEOLOGY. 


I 


W\ 


highly  differentiated  "  Cortlandt  Series,"  near  Peekskill,  presents 
us  with  the  deeply  eroded  roots  of  an  ancient  volcano,  probably 
of  Cambrian  or  Silurian  age,  whose  superficial  parts  have  entirely 
disappeared.'  The  eleolite-syenite  area  in  northern  New  Jersey 
is  probably  of  the  same  character. 

In  Pennsylvania  and  Maryland  we  find  in  the  South   Moun- 
tain or  Blue  Ridge,  between   Harrisburg  and  the  Potomac,  one 
of  the  most  highly  diversified  and  perfectly  preserved  areas  of 
pre-Cambrian  volcanic  rocks  in  the  world.     Its  position  is  estab- 
lished as  below  the  Olenellus  sandstone ;  it  presents  both  acid 
(rhyolitic)  and  basic  (basaltic)  types;  it  exhibits  within  limited 
shear-zones  the  plainest  effects  of  dynamic  action,  but  its  great 
mass  is   nevertheless  so  little   changed  that  each    microscopic 
structure   of    glassy   rocks   is  clearly    recognizable.      Skeleton 
crystals,  minute  pores  and  larger  vesicles,  protoclastic  breaking 
of  the    phenocrysts,    fluidal  structures  of   every  kind,  trichites, 
spherulites,  axiolites,  lithophysal   and  perlitic  parting  have  lost 
none  of  their  original  sharpness,  in  spite  of  the  complete  devitri- 
fication of  the  glassy  base.     Most  of  the   rocks  were  probably 
always  wholly  or  mostly  crystalline,  but  some  regions,  like  the 
Bigham  Copper  and  Raccoon  Creek,  display  the  old  spherulitic 
obsidians  and  pumice  in  a  manner  allowing  of  no  doubt.     The 
pyroclastic  materials  accompanying  these  old  lavas  are  also  finely 
developed — ash-beds,  coarse  and  fine  flow-  and  tuff-breccias,  etc. 
The  precise  centers  A  eruption  within  this  region  have  not  yet  been 
definitely  located,  but   with  what  has  already  been    published 
regarding  these  rocks  and  the  further  details  which  may  be  soon 
expected,  no  further  description  of  them  is  here  necessary."    The 
entire  misunderstanding  of  these  rocks  by  Rogers,  Hunt,  Lesley 
and  Fraser,  who  interpreted  them  as  altered  slates  and  their  sec- 
ondary cleavage  as  bedding,  has  greatly  retarded  the  solution 

»  Professor  Dana  once  suggested  that  the  Cortlandt  massive  rocks  might  have 
been  formed  by  the  metamorphism  of  " volcanic  debris  or  cinders"  (Am.  Jour,  of 
Science,  3d  sen.  Vol.  22,  p.  112,  Aug.  1881),  but  he  subsequently  admitted  their  intru- 
sive character  (ib.  Vol.  28,  p.  384,  Nov.  1884).  See  also  opinions  of  the  present  writer 
(ib.  Vol.  36,  p.  268,  Oct,  1888). 

"Am.  Jour,  of  Science  (3rd  ser.)  Vol.  44,  December,  1892,  and  Vol.  46,  July,  1893. 


1 


THE  DISTRIBUTION  OF  ANCIENT  VOLCANIC  ROCKS.    27 

of  the  geology  of  South  Mountain,  and  has  for  many  years 
invested  it  with  a  reputation  for  complexity  which  it  in  no  way 
deserves.' 

In  Maryland  and  Virginia  the  acid  and  basic  lavas  and  tuffs 
of  South  Mountain  are  extended  southward  as  an  important  ele- 
ment in  the  composition  of  the  Blue  Ridge.  They  have  been 
somewhat  studied  by  the  writer  in  this  region  and  have  been 
mapped  and  described  by  Keith.'  This  author  mentions  two 
quartz-porphyry  areas  showing  flow-structure  and  tuffs,  the 
larger  between  Catoctin  and  Blue  mountains  in  Maryland,'  and 
the  smaller  near  Front  Royal  in  Virginia.  He  says  that  the 
diabase  shows  many  indications  of  being  a  surface  flow,  and  that 
it  extends  along  the  Blue  Ridge  from  Maryland  half  way  across 
Virginia,  with  an  average  width  of  twenty  miles. 

Southern  States.— MoXc^mc  rocks  are  largely  developed  in  the 
central  portion  of  both  the  Carolinas,  as  may  be  gathered  from 
the  old  reports  of  Emmons  and  Lieber.     During  the  past  sum- 
mer the  writer  had  the  opportunity  of  examining  the   belt  in 
Chatham  and  Orange  counties,  North  Carolina,  in  company  with 
the  State  Geologist,  Professor  J.  A.  Holmes.     The  time  at  com- 
mand was  inadequate  for  the  thorough  exploration  of  the  vol- 
canic belt  which  skirts  the  western  edge  of  the Triassic  sandstone, 
but  in  a  drive  from  Sanford  to  Chapel  Hill  an  abundance  of  the 
most  typical  ancient  lavas,  mostly  of  the  acid  type,  was  encoun- 
tered.    On  the  road  from  Sanford  to  Pittsboro   purple   felsites 
and  porphyries  showing  spherulites  and  beautiful  flow-structures, 
and  accompanied  by  pyroclastic  breccias  and  tuffs,  were  met  with 
two  miles  north  of  Deep  river  and  were  almost  continuously 
exposed   to    Rocky  river.     Here    devitrified  acid   glasses   with 
chains  of  spherulites  and  eutaxitic  structure  were  collected,  while 
beyond  as  far  as  Bynum  on   Haw  river,  four  miles  northeast  of 

1892!^'*^"  ^'^^^^^^-  Summary  Final  Report,  Penn.  Geol.  Survey,  Vol.   i,  p.  151, 

"American  Geologist,  Vol.  10,  pp.  366-68,  December,  1892.  Geologic  Atlas  of 
the  U.  S.,  Harper's  Ferry  Sheet  {in  press).  For  their  distribution  in  Maryland  see  the 
Geological  Map  of  the  State,  edited  by  G.  H.  Williams,  and  published  in  the 
World's  Fair  Book  "  Maryland,"  Baltimore,  1893. 


auM 


^•.^^ra.. 


Fi 


I' 


r 


28 


THE  JOURNAL  OF  GEOLOGY. 


Pittsboro,  the  only  rocks  seen  were  of  the  same  general  charac- 
ter.    On  the  farm  of  Spence  Taylor,  Esq.,  in  Pittsboro,  a  bright 
red  porphyry  with  flow  lines  is  exposed  in  so  altered  a  condition 
that  it  can  be  easily  cut  into  any  form  with  a  knife,  though  it 
still  preserves  all  the  details  of  its  structure.     It  looks  not  unhke 
the  well  known    pipe-stone,  or    Catlinite  of  Minnesota.     Three 
quarters  of  a  mile  beyond  Pittsboro  on  the  Bynum  road  there  is 
a  considerable  exposure  of  a  basic  amygdaloid.     South  of  Hack- 
ney's Cross  Roads  there  are  other  excellent  exposures  of  the 
ancient  rhyolites    with    finely    developed    spherulitic  and  flow- 
structures.      Numerous   specimens   were   here   collected   which 
place  the  character  of  these  rocks  as  surface    flows   beyond   a 
doubt.     Another  locality    in   the   volcanic   belt  was  visited  on 
Morgan's  Run,  about  two  miles  south  of  Chapel  Hill.     Here  are 
to  be  seen  admirable  exposures  of  volcanic  flows  and  breccias 
with  finer  tuff  deposits,  which  have  been  extensively  sheared  into 
slates  by  dynamic  agency.     Toward  the  east  and  north  these 
rocks  pass  under  the  transgression  of  Newark  sandstone.     The 
accompanying  sketch-map  (Fig.  2)  shows  the  relations  of  the 
above  mentioned   localities  in  Chatham    and   Orange   counties, 
N.  C.     From  still  another  locality  at  the    cross-road    near  the 
northern  boundary  of  Chatham  county,  fifteen  miles  southwest 
of   Chapel   Hill,    Professor    Holmes   informs   me   specimens  of 
undoubted  volcanic  rocks  have   recently  been  secured  ;  he  has 
also   sent   to   me   within   the    past    month    a   suite   of    similar 
specimens  from  Pace's  Bridge  on  Haw  river,  three  miles  above 

Bynum.  u  r- 

In  his  upper  division  of  the  Taconic  System  in  North  Caro- 
lina, Emmons  describes  numerous  beds  of  "  chert  or  hornstone" 
intercalated  in  the  slates  and  sometimes  forming  isolated  bosses, 
whose  origin  he  is  at  a  loss  to  account  for.  He  says  they  are 
not  metamorphic,  but  does  not  suggest  for  them  an  igneous  ori- 
gin.' The  hypothesis  that  these  rocks  may  also  be  of  volcanic 
origin  is  sustained  by  Emmons'  description  of  "brecciated  con- 
glomerates" associated  with  the  chert  beds,  which  are  composed 
■Geological  Report  of  the  Mull^.d  Counties,  N.  C,  1856,  pp.  66-68. 


% 


charac- 
bright 
ndition 
ough  it 
t  unlike 
Three 
there  is 
f  Hack- 
of  the 
id  flow- 
1   which 
;yond    a 
jited  on 
I  ere  are 
breccias 
ired  into 
th  these 
le.     The 
s  of  the 
counties, 
near  the 
outhwest 
imens  of 
;  he  has 
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rth  Caro- 
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:d  bosses, 

they  are 
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volcanic 
ated  con- 
:omposed 


THE  DISTRIBUTION  OF  ANCIENT  VOLCANIC  ROCKS.    29 

of  an  argillaceous  or  chloritic  base,  containing  angular  chert  frag- 
ments of  all  sizes  up  to  two  feet.     He  mentions  many  localities 


ScoU  of  Miles  • 


Fig.  2. 
Fig.  2.     Sketch  map  of  parts  of  Chatham  and  Orange  counties,  N.  C,  showing  locali- 
ties for  ancient  volcanic  rocks. 

for   these   rocks,  most  of  which   are   near  the  Yadkin  river  in 
Davidson,  Rowan  and  Montgomery  counties. 

I  am  informed  by  Mr.  Arthur  Keith  that  he   discovered  a 


ir-mfc; 


30 


THE  JOURNAL  OF  GEOLOGY. 


i!  I 


%■'    ' 


large  area  of  quartz-porphyry  in  the  Great  Smoky  Mountains  in 
Yancey  Co.,  N.  C,  during  the  past  summer. 

The  geological  reports  on  South  Carolina,  by  Lieber,  describe 
a  great  development  of  igneous  rocks  which  cross  the  state  in 
the  continuation  of  the  North  Carolina  volcanic  belt  and  which 
are  themselves  very  probably  in  part  of  surface  origin.  His  first 
report  for  1856,  which  treats  of  Chesterfield,  Lancaster,  Chester 
and  York  counties,  mentions  among  other  more  coarsely  gran- 
ular igneous  rocks,  eurite  or  quartz-porphyry,  aphanitic-porphyry 
and  melaphyre.'  The  counties  of  Union  and  Spartanburg,  dealt 
with  in  Lieber's  second  report,  are  much  poorer  in  igneous  rocks, 
though  he  here  adds  the  types  schistose  aphanite  and  minette. 
On  the  geological  map  of  South  Carolina,  published  by  the 
Department  of  Agriculture  in  1883,  the  belt  of  aphanitic  green- 
stones and  porphyries  is  shown  to  be  continuous  across  the  state 
in  a  southwest  direction,  and  the  statement  is  made  that  the 
greenstones  predominate  toward  the  north,  and  the  porphyries 
towrrd  the  south,  in  Abbeville  county. 

Upon  an  expedition  undertaken  at  the  instigation  of  the 
writer.  Prof.  S.  L.  Powell  of  Newbury,  S.  C,  found  at  Chester 
abundant  eruptive  rocks  (granites  and  diorites),  but  none  of 
unmistakably  volcanic  origin.  At  Lancaster,  on  the  other  hand, 
he  found  amygdaloids  and  felsites,  showing  distinct  flow-struct- 
ures which  are  certainly  of  igneous  origin  and  could  only  have 
solidified  at  the  surface. 

In  Georgia  and  Alabama  nothing  can  be  stated  with  cer- 
tainty in  regard  to  ancient  volcanic  rocks  as  the  crystalline 
portions  of  these  states  have  not  as  yet  been  petrographically 
investigated.  The  porphyry  area  of  Abbeville  county,  S.  C,  is 
probably  continued  into  Georgia.  One  single  specimen  of  quartz- 
porphyry  showing-  a  beautiful  micropoikilitic  structure,  collected 
in  northwestern  Georgia  near  the  Tennessee  line,  has  already 
been  mentioned  by  the  writer.'     A  box  of  specimens  kindly  sent 

«  Report  on  the  Survey  of  South  Carolina  for  1856,  2d  ed.,  Columbia,  1858.  p.  31. 
Lieber  had  the  German  ideas  regarding  igneous  rocks  and  their  nomenclature.  His 
"  trachyte,"  "  domite  "  and  "  phonolite  "  are  probably  fine  grained  varieties  of  the 
acid  volcanic  types. 


k 


IL 


THE  DISTRIBUTION  OF  ANCIENT  VOLCANIC  ROCKS.    3  I 

to  me  for  examinativ-ij  by  Professor  Eugene  Smith  of  Alabama, 
proved  to  contain  nothing  which  could  be  identified  as  ancient 
volcanic  material. 

OENERAL  CONCLUSIONS. 

The  above  rapid  survey  of  the  now  known  and  probable  areas 
of  ancient  volcanic  rocks  in  the  crystalline  portion  of  the  Appa- 
lachian system  reveals  the  fact  that  this  cla.ss  of  material  is 
both  abundant  and  widely  distributed.  From  Newfoundland  to 
Georgia  it  has  been  identified.  For  many  areas  the  evidence  of 
surface  or  volcanic  origin  is  conclusive,  while  in  many  others  it 
Ij  as  yet  only  probable. 

The  areas  of  these  ancient  volcanic  ro'cks  now  known  fall 
roughly  in  two  parallel  belts  (see  map);  of  these  the  eastern 
embraces  the  exposures  of  Newfoundland,  Cape  Breton,  Nova 
Scotia,  the  Bay  of  Fundy,  Coast  of  Maine,  Boston  basin  and  the 
central  Carolinas  ;  while  the  western  belt  crosses  the  Eastern 
Townships  and  follows  the  Blue  Ridge  through  southern  Penn- 
sylvania, Maryland,  Virginia,  North  Carolina  to  Georgia. 

The  purpose  of  the  present  communication  will  be  accom- 
plished if  it  succeeds  in  directing  attention  to  this  group  of 
rocks.  New  areas  should  be  added  ;  probable  areas  investigated  ; 
and  known  areas  monographed  all  along  this  old  mountain  range. 
How  fruitful  a  field  is  here  spread  out  to  students  of  geology 
and  petrography  may  be  seen  from  the  results  of  work  in  anal- 
ogous regions  by  Harker"  and  Mugge.s 

The  identification  of  truly  volcanic  rocks  in  highly  or  partly 
crystalline  terrains  possesses  far  more  than  a  petrographical  sig- 
nificance, since  by  fixing  what  was  the  surface  at  the  time  of 
their  formation,  they  furnish  a  certain  datum  for  tracing  out  the 
sequence  of  later  geographic  changes  and  geological  develop- 
'"^"*-  George  Huntington  Williams. 

'  Am.  Jour,  of  Science  (3d  ser.)  Vol.  46,  p.  47,  July,  1893 ;  and  this  Journa!,  Vol.  t 
P-  179,  1893. 

'The  Bala  Volcanic  Series  of  Caernarvonshire,  Sedgwick  prize  essay  for  1888  by 
A.  Marker,  Cambridge,  1889.  ' 

3  Untersuchungen  uber  die  "  Lenneporphyre  "  in  Westfalen  und  den  an.?renzendtn 
GebietenbyO.  Mugge.  Neues  Jahrbuch  fUr  Min.,  etc.,  Beilage  Band  vui  dd  czr- 
721.  1893.  •  HH  3  5 


